Fix 'use-implicit-booleaness' wrongly emitted for generators. (#10107) (#10109)

Co-authored-by: Nedelcu <Nedelcu Ioan-Andrei>
Co-authored-by: Pierre Sassoulas <pierre.sassoulas@gmail.com>
(cherry picked from commit a4e91d7)

Co-authored-by: Nedelcu Ioan-Andrei <138256980+nedelcu-ioan@users.noreply.github.com>

Author: github-actions[bot]

doc/whatsnew/fragments/10100.false_positive

@@ -0,0 +1,4 @@
+Fix a false positive for `use-implicit-booleaness-not-len`. No lint should be emitted for
+generators (`len` is not defined for generators).
+
+Refs #10100

pylint/checkers/refactoring/implicit_booleaness_checker.py

@@ -125,14 +125,8 @@ def visit_call(self, node: nodes.Call) -> None:
         if not utils.is_test_condition(node, parent):
             return
         len_arg = node.args[0]
-        generator_or_comprehension = (
-            nodes.ListComp,
-            nodes.SetComp,
-            nodes.DictComp,
-            nodes.GeneratorExp,
-        )
-        if isinstance(len_arg, generator_or_comprehension):
-            # The node is a generator or comprehension as in len([x for x in ...])
+        if isinstance(len_arg, (nodes.ListComp, nodes.SetComp, nodes.DictComp)):
+            # The node is a comprehension as in len([x for x in ...])
             self.add_message(
                 "use-implicit-booleaness-not-len",
                 node=node,

tests/functional/u/use/use_implicit_booleaness_not_len.py

@@ -125,7 +125,7 @@ class ChildClassWithoutBool(ClassWithoutBool):
     assert len(ChildClassWithoutBool())  # [use-implicit-booleaness-not-len]
     assert len(range(0))  # [use-implicit-booleaness-not-len]
     assert len([t + 1 for t in []])  # [use-implicit-booleaness-not-len]
-    assert len(u + 1 for u in [])  # [use-implicit-booleaness-not-len]
+    assert len(u + 1 for u in [])  # Should be fine
     assert len({"1":(v + 1) for v in {}})  # [use-implicit-booleaness-not-len]
     assert len(set((w + 1) for w in set()))  # [use-implicit-booleaness-not-len]
 
@@ -189,3 +189,7 @@ def github_issue_4215():
 
 if len('TEST'):
     pass
+
+def github_issue_10100():
+    if len((x for x in [1, 2, 3])):  # Should be fine
+        print("yay!")

tests/functional/u/use/use_implicit_booleaness_not_len.txt

@@ -18,7 +18,6 @@ use-implicit-booleaness-not-len:124:11:124:34:github_issue_1879:Do not use `len(
 use-implicit-booleaness-not-len:125:11:125:39:github_issue_1879:Do not use `len(SEQUENCE)` without comparison to determine if a sequence is empty:INFERENCE
 use-implicit-booleaness-not-len:126:11:126:24:github_issue_1879:Do not use `len(SEQUENCE)` without comparison to determine if a sequence is empty:INFERENCE
 use-implicit-booleaness-not-len:127:11:127:35:github_issue_1879:Do not use `len(SEQUENCE)` without comparison to determine if a sequence is empty:HIGH
-use-implicit-booleaness-not-len:128:11:128:33:github_issue_1879:Do not use `len(SEQUENCE)` without comparison to determine if a sequence is empty:HIGH
 use-implicit-booleaness-not-len:129:11:129:41:github_issue_1879:Do not use `len(SEQUENCE)` without comparison to determine if a sequence is empty:HIGH
 use-implicit-booleaness-not-len:130:11:130:43:github_issue_1879:Do not use `len(SEQUENCE)` without comparison to determine if a sequence is empty:INFERENCE
 use-implicit-booleaness-not-len:171:11:171:42:github_issue_1879:Do not use `len(SEQUENCE)` without comparison to determine if a sequence is empty:INFERENCE